1. Field of the Invention
The present invention is directed generally to the field of electronic component subassemblies. More specifically, the present invention is directed to improved structures and methods for forming Hall effect sensor elements with integral EMI shielding capacitors.
2. Description of the Related Art
Electronic sensors are widely used in a variety of applications. The demand and use for these sensors is currently growing at a rapid rate. However, as with most electronic devices, there is an ever increasing demand for simplified manufacturing processes as well as decreasing the physical size of the device packages. Currently, typical Hall effect sensor elements overcome problems associated with electromagnetic interference (EMI) and electro static discharge (ESD) through the use of bypass capacitors appropriately connected to the Hall effect sensor elements. In these known designs, capacitors are connected by some method of soldering, welding, etc. to form an operational electronic subassembly to be used in the manufacture of automotive or other sensors.
During these known manufacturing processes, it is necessary that a device or person accurately grasps and positions each of the components during the connection process. Typically, epoxy clad radial lead capacitors are chosen for their desired packaging. However, the relatively large size of these components and their often irregular body shape make them less than optimal for achieving the goals of improving the manufacturing process and minimizing the overall size of the sensor package. Furthermore, in terms of performance, EMI suppression and ESD protection are enhanced by locating the capacitors physically closer to the Hall element than is typically possible with this type of capacitor package.
Due to the limitations imposed by the large capacitor bodies, the ability to achieve the desired results is limited in these prior systems. Although much smaller capacitor packages are currently available, their size is disproportionate to the equipment in the sensor assembly process and the fragile structure requires protection from damage by subsequent processing of the overall package. Thus, existing packaging solutions have limitation in their current requirement to use their relatively sized epoxy clad radial lead capacitors.
Accordingly, there remains a need in the art to improve manufacturing processes of Hall effect sensor assemblies through decreasing the physical size of the overall assembly. Additionally, there remains a need in the art to improve the manufacturing process associated with Hall effect assemblies. Other objects and advantages of the present invention will be apparent from the following summary and detailed description of the preferred embodiments.
In accordance with the present invention, in order to decrease the overall package size of the Hall effect sensor element and improve the manufacturing process, leadless chip type capacitors are employed as EMI shielding/ESD protection and bypass capacitors. The problems identified above that were associated with the use of these smaller components are overcome by the use of a carrier package in one embodiment of the present invention. In an alternate embodiment, an insulated, molded encapsulation is applied and surrounds the chip capacitors and the connections to the Hall effect sensor.
In a first exemplary embodiment of the present invention, a molded carrier structure provides a housing for mounting a Hall cell element as well as one or more EMI shielding/ESD protection or bypass capacitors. The carrier housing facilitates interconnection of the Hall cell and the chip capacitor. Additionally, this structure simplifies the manufacturing process for connection of the smaller leadless chip capacitor components.
In one exemplary embodiment, the Hall cell is cradled in extended arms of the carrier housing. Leads from the Hall cell are received within cavities of the carrier and one or more chip capacitors are received in a further cavity formed within the carrier housing. The carrier housing is comprised of a molded insulative body, preferably formed from heat resistant plastic. Although it is not necessary, it is preferred that a plurality of individual cavities be formed in order to facilitate the easy placement of each of the individual chip capacitor components as well as protection for the overall assembly. The Hall cell and leads and one or more leadless chip capacitors are placed in their appropriate cavities of the carrier housing during the manufacturing process. Subsequently, the necessary solder connections are formed to provide electrical contact between the Hall cell and EMI shielding/ESD protection bypass capacitors.
In one alternate embodiment of the invention, the chip carrier housing includes a spring pressure element which applies pressure between the leads of the Hall cell and the leadless chip carrier elements. This ensures better electrical contact between the respective elements. After the leadless chip capacitors have been soldered to the appropriate leads of the Hall cell, epoxy or other insulative material is applied to fill in the remaining spaces of the cavities thereby providing a more durable physical package.
In an alternate embodiment, the Hall cell has leads which protrude from its body on which one or more EMI shielding/ESD protection bypass capacitors are mounted. These bypass capacitors are desirably leadless chip type capacitors. Once the leadless chip type capacitors have been soldered to their respective leads from the Hall cell, an epoxy or other insulative encapsulation is applied, preferably within a mold to surround the chip capacitors and leads. The use of chip capacitors in either embodiment provides an overall smaller package for the Hall effect sensor.